Multilayer ceramic capacitor and manufacturing method of multilayer ceramic capacitor

ABSTRACT

A multilayer ceramic capacitor includes: a multilayer structure in which each of a plurality of dielectric layers and each of a plurality of internal electrode layers are alternately stacked, wherein concentrations of Mn, Si and B of a margin region are respectively higher than concentrations of Mn, Si and B of the dielectric layers, wherein a donor element concentration of the margin region is lower than a donor element concentration of the dielectric layers, wherein the margin region is at least one of an end margin region and a side margin region.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority of theprior Japanese Patent Application No. 2018-096107, filed on May 18,2018, the entire contents of which are incorporated herein by reference.

FIELD

A certain aspect of the present invention relates to a multilayerceramic capacitor and a manufacturing method of the multilayer ceramiccapacitor.

BACKGROUND

Recently, electronic devices such as smart phones or mobile phones arebeing downsized. Thereby, electronic components mounted on theelectronic devices are rapidly being downsized. For example, in a fieldof a multilayer ceramic capacitor, thicknesses of dielectric layers andinternal electrodes are reduced in order to reduce a chip size.

When the thickness of the dielectric layer is reduced, a voltage appliedto each dielectric layer increases. In this case, a lifetime of thedielectric layer may be shortened. And, reliability of the multilayerceramic capacitor may be degraded. And so, there are disclosedtechnologies in which a donor element such as Mo (molybdenum), Nb(niobium), Ta (tantalum) or W (tungsten) is added to the dielectriclayer (for example, see Japanese Patent Application Publications No.2016-127120, No. 2016-139720, No. 2017-028224 and No. 2017-028225).

When the thickness of the dielectric layer is reduced, the number of thedielectric layers increases. For example, the multilayer ceramiccapacitor has a structure in which each of dielectric layers and each ofinternal electrode layers are alternately stacked. However, the internalelectrode layer does not cover the whole of the dielectric layer inorder that the internal electrode is not exposed to the side face of thechip. In this case, the internal electrode layer only extends to insideof a circumference of the dielectric layer. Therefore, a leveldifference occurs between a capacity region in which the dielectriclayers and the internal electrode layers are alternately stacked and aside margin region in which the dielectric layers are stacked withoutsandwiching the internal electrode layers. And, when the number of thedielectric layers increases, a structural defect such as delaminationeasily occurs because of the level difference.

As a method of solving the problem, there is disclosed a method in whichthe level difference is absorbed by printing an internal electrodepattern on a ceramic green sheet and printing a reverse pattern ofceramic paste on a part of the green sheet where the internal electrodepattern is not printed.

However, with the method, a micro clearance may occur between an end ofthe internal electrode layers and the side margin region because of adifference of contraction in sintering between the capacity region andthe side margin region. In this case, a water component such as moistureintrudes into the clearance and humidity resistance is degraded.Therefore, high reliability may not be necessarily achieved.

And so, there is disclosed a method in which the difference ofcontraction in sintering is reduced by covering ceramic powder used fora ceramic green sheet for absorbing the level difference, with a glassfilm (for example, see Japanese Patent Application Publication No.2004-96010). And, there is disclosed a method in which humidityresistance is improved by increasing a Mg concentration of a gap on theside of a face side more than a Mg concentration of an effective layerportion contributing a capacity (for example, see Japanese PatentApplication Publication No. 2010-103566).

SUMMARY OF THE INVENTION

However, it is not possible to sufficiently improve the reliability withthe above-mentioned methods.

The present invention has a purpose of providing a multilayer ceramiccapacitor and a manufacturing method of the multilayer ceramic capacitorthat are capable of sufficiently improving reliability thereof.

According to an aspect of the present invention, there is provided amultilayer ceramic capacitor including: a multilayer structure in whicheach of a plurality of dielectric layers and each of a plurality ofinternal electrode layers are alternately stacked, a main component ofthe dielectric layers being ceramic, the multilayer structure having arectangular parallelepiped shape, the plurality of internal electrodelayers being alternately exposed to a first end face and a second endface of the multilayer structure, the first end face facing with thesecond end face, wherein concentrations of Mn, Si and B of a marginregion with respect to a main component ceramic of the margin region arerespectively higher than concentrations of Mn, Si and B of thedielectric layers in the multilayer structure with respect to a maincomponent ceramic of the dielectric layers in the multilayer structure,wherein a donor element concentration of the margin region with respectto the main component ceramic of the margin region is lower than a donorelement concentration of the dielectric layers in the multilayerstructure with respect to the main component ceramic of the dielectriclayers in the multilayer structure, wherein the margin region is atleast one of an end margin region and a side margin region, wherein, inthe multilayer structure, the end margin region is a region in whichinternal electrode layers exposed to the first end face are facing witheach other without sandwiching an internal electrode layer exposed tothe second end face and a region in which internal electrode layersexposed to the second end face are facing with each other withoutsandwiching an internal electrode layer exposed to the first end face,wherein, in the multilayer structure, the side margin is a regioncovering edge portions to which the plurality of internal electrodelayers extend toward two side faces other than the first end face andthe second end face.

According to another aspect of the present invention, there is provideda manufacturing method of a multilayer ceramic capacitor including: afirst process of providing a first pattern of metal conductive paste, ona green sheet including main component ceramic grains; a second processof making a stack unit by providing a second pattern of main componentceramic grains, around the first pattern on the green sheet; and a thirdprocess of stacking a plurality of the stack units formed in the secondprocess so that positions of the first patterns are alternately shiftedto each other and firing a ceramic multilayer structure of the stackunits, wherein concentrations of Mn, Si and B of the second pattern withrespect to a main component ceramic of the second pattern arerespectively higher than concentrations of Mn, Si and B of the greensheet with respect to a main component ceramic of the green sheet,wherein a donor element concentration of the second pattern with respectto the main component ceramic of the second pattern is lower than adonor element concentration of the green sheet with respect to the maincomponent ceramic of the green sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a partial perspective view of a multilayer ceramiccapacitor;

FIG. 2 illustrates a cross sectional view taken along a line A-A of FIG.1;

FIG. 3 illustrates a cross sectional view taken along a line B-B of FIG.1;

FIG. 4A illustrates an enlarged view of a cross section of a side marginregion;

FIG. 4B illustrates an enlarged view of a cross section of an end marginregion; and

FIG. 5 illustrates a manufacturing method of a multilayer ceramiccapacitor.

DETAILED DESCRIPTION

A description will be given of an embodiment with reference to theaccompanying drawings.

(Embodiment) FIG. 1 illustrates a partial perspective view of amultilayer ceramic capacitor 100 in accordance with an embodiment. FIG.2 illustrates a cross sectional view taken along a line A-A of FIG. 1.FIG. 3 illustrates a cross sectional view taken along a line B-B ofFIG. 1. As illustrated in FIG. 1 to FIG. 3, the multilayer ceramiccapacitor 100 includes a multilayer chip 10 having a rectangularparallelepiped shape, and a pair of external electrodes 20 a and 20 bthat are respectively provided at two end faces of the multilayer chip10 facing each other. In four faces other than the two end faces of themultilayer chip 10, two faces other than an upper face and a lower faceof the multilayer chip 10 in a stacking direction are referred to asside faces. The external electrodes 20 a and 20 b extend to the upperface, the lower face and the two side faces of the multilayer chip 10.However, the external electrodes 20 a and 20 b are spaced from eachother.

The multilayer chip 10 has a structure designed to have dielectriclayers 11 and internal electrode layers 12 alternately stacked. Thedielectric layer 11 includes ceramic material acting as a dielectricmaterial. The internal electrode layers 12 include a base metalmaterial. End edges of the internal electrode layers 12 are alternatelyexposed to a first end face of the multilayer chip 10 and a second endface of the multilayer chip 10 that is different from the first endface. In the embodiment, the first end face faces with the second endface. The external electrode 20 a is provided on the first end face. Theexternal electrode 20 b is provided on the second end face. Thus, theinternal electrode layers 12 are alternately conducted to the externalelectrode 20 a and the external electrode 20 b. Thus, the multilayerceramic capacitor 100 has a structure in which a plurality of dielectriclayers 11 are stacked and each two of the dielectric layers 11 sandwichthe internal electrode layer 12. In a multilayer structure of thedielectric layers 11 and the internal electrode layers 12, the internalelectrode layer 12 is positioned at an outermost layer in a stackingdirection. The upper face and the lower face of the multilayer structurethat are the internal electrode layers 12 are covered by cover layers13. A main component of the cover layer 13 is a ceramic material. Forexample, a main component of the cover layer 13 is the same as that ofthe dielectric layer 11.

For example, the multilayer ceramic capacitor 100 may have a length of0.25 mm, a width of 0.125 mm and a height of 0.125 mm. The multilayerceramic capacitor 100 may have a length of 0.4 mm, a width of 0.2 mm anda height of 0.2 mm. The multilayer ceramic capacitor 100 may have alength of 0.6 mm, a width of 0.3 mm and a height of 0.3 mm. Themultilayer ceramic capacitor 100 may have a length of 1.0 mm, a width of0.5 mm and a height of 0.5 mm. The multilayer ceramic capacitor 100 mayhave a length of 3.2 mm, a width of 1.6 mm and a height of 1.6 mm. Themultilayer ceramic capacitor 100 may have a length of 4.5 mm, a width of3.2 mm and a height of 2.5 mm. However, the size of the multilayerceramic capacitor 100 is not limited.

A main component of the internal electrode layers 12 is a base metalsuch as nickel (Ni), copper (Cu), tin (Sn) or the like. The internalelectrode layers 12 may be made of a noble metal such as platinum (Pt),palladium (Pd), silver (Ag), gold (Au) or alloy thereof. The dielectriclayers 11 are mainly composed of a ceramic material that is expressed bya general formula ABO₃ and has a perovskite structure. The perovskitestructure includes ABO_(3-α) having an off-stoichiometric composition.For example, the ceramic material is such as BaTiO₃ (barium titanate),CaZrO₃ (calcium zirconate), CaTiOZ₃ (calcium titanate), SrTiO₃(strontium titanate), Ba_(1-x-y)Ca_(x)Sr_(y)Ti_(1-z)Zr_(z)O₃ (0≤x≤1,0≤y≤1, 0≤z≤1) having a perovskite structure.

As illustrated in FIG. 2, a region, in which a set of the internalelectrode layers 12 connected to the external electrode 20 a faceanother set of the internal electrode layers 12 connected to theexternal electrode 20 b, is a region generating electrical capacity inthe multilayer ceramic capacitor 100. And so, the region is referred toas a capacity region 14. That is, the capacity region 14 is a region inwhich the internal electrode layers 12 next to each other beingconnected to different external electrodes face each other.

A region, in which the internal electrode layers 12 connected to theexternal electrode 20 a face with each other without sandwiching theinternal electrode layer 12 connected to the external electrode 20 b, isreferred to as an end margin region 15. A region, in which the internalelectrode layers 12 connected to the external electrode 20 b face witheach other without sandwiching the internal electrode layer 12 connectedto the external electrode 20 a is another end margin region 15. That is,the end margin region 15 is a region in which a set of the internalelectrode layers 12 connected to one external electrode face with eachother without sandwiching the internal electrode layer 12 connected tothe other external electrode. The end margin region 15 is a region thatdoes not generate electrical capacity in the multilayer ceramiccapacitor 100.

As illustrated in FIG. 3, a region of the multilayer chip 10 from thetwo sides thereof to the internal electrode layers 12 is referred to asa side margin region 16. That is, the side margin region 16 is a regioncovering edges of the stacked internal electrode layers 12 in theextension direction toward the two side faces.

FIG. 4A illustrates an enlarged view of the cross section of the sidemargin region 16. The side margin region 16 has a structure in which thedielectric layer 11 and a reverse pattern layer 17 are alternatelystacked in a stacking direction of the dielectric layer 11 and theinternal electrode layer 12 in the capacity region 14. Each of thedielectric layers 11 of the capacity region 14 are continuously formedwith each of the dielectric layers 11 of the side margin region 16. Withthe structure, a level difference between the capacity region 14 and theside margin region 16 is suppressed.

FIG. 4B illustrates an enlarged view of the cross section of the endmargin region 15. Compared to the side margin region 16, in the endmargin region 15, every other layer, the internal electrode layers 12extends to the edge face of the end margin region 15. The reversepattern layer 17 is not provided in a layer where the internal electrodelayer 12 extends to the end face of the end margin region 15. Each ofthe dielectric layers 11 of the capacity region 14 is continuouslyformed with each of the dielectric layers 11 of the end margin region15. With the structure, a level difference between the capacity region14 and the end margin region 15 is suppressed.

The dielectric layer 11 is formed by firing raw material powder of whicha main component ceramic has a perovskite structure. The raw materialpowder is exposed to reductive atmosphere during the firing. Therefore,oxygen defect occurs in the main component ceramic. And so, it isthought that Mo, Nb, Ta, W or the like acting as a donor is added to thedielectric layer 11 in order to displace the B site of the perovskitestructure expressed by ABO₃ with the donor element. When the donorelement is added to the dielectric layer 11, formation of the oxygendefect of the main component ceramic may be suppressed. Therefore, thelife characteristic of the dielectric layer 11 is improved, thereliability is improved, a high dielectric constant is achieved, andpreferable bias characteristic is achieved. However, when a large amountof the donor element is added to the reverse pattern layer 17, thestructural defect caused by the delay of sintering may occur because ofthe abnormal grain growth at the surface of the multilayer chip 10caused by the promotion of the grain growth of the main componentceramic or prevention of densifying caused by the abnormal grain growth.Alternatively, when a large amount of the donor element is added to thereverse pattern layer 17, the structural defect caused by spheroidizingof the internal electrode layer 12 near the reverse pattern layer 17 mayoccur because the grain growth of the reverse pattern layer 17 ispromoted. Therefore, the reliability of the multilayer ceramic capacitor100 may be degraded. For example, the humidity resistance is degradedbecause of the prevention of the densifying. Increasing of a short rate,reduction of the lifetime, reduction of BDV (Breakdown Voltage) or thelike may occur because of the structural defect caused by thespheroidizing.

And so, in the embodiment, a donor element concentration in the reversepattern layer 17 with respect to the main component ceramic of thereverse pattern layer 17 is lower than a donor concentration in thedielectric layer 11 with respect to the main component ceramic of thedielectric layer 11. With the structure, abnormal grain growth or delayof sintering at the surface of the multilayer chip 10 is suppressed.Thereby, structural defect is suppressed. Therefore, the reliability ofthe multilayer ceramic capacitor 100 is improved.

Because of diffusion of the donor element during the firing, the donorelement concentration of the whole of the end margin region 15 and theside margin region 16 (hereinafter referred to as a margin region) withrespect to the main component ceramic of the end margin region is lowerthan the donor element concentration of the dielectric layer 11 in thecapacity region 14 with respect to the main component ceramic of thedielectric layer 11.

Next, during the firing, because of a difference between sinteringcharacteristic of a metal and sintering characteristic of a ceramicmaterial, a difference may occur in contraction in sintering between theinternal electrode layer 12 and the reverse pattern layer 17. Inconcrete, the sintering characteristic of the internal electrode layer12 is higher than the sintering characteristic of the reverse patternlayer 17. Therefore, a micro clearance may occur between the end of theinternal electrode layer 12 and the reverse pattern layer 17. When awater component such as humidity intrudes into the clearance, humiditydefect may occur. Thus, the reliability of the multilayer ceramiccapacitor 100 may be degraded. In the description, when the sinteringcharacteristic is high, a temperature at which the contraction(densifying) terminates is low.

And so, in the embodiment, a concentration of a sintering assistant ofthe reverse pattern layer 17 is higher than a concentration of asintering assistant of the dielectric layer 11. In concrete,concentrations of Mn (manganese), Si (silicon) and B (boron) of thereverse pattern layer 17 are higher than concentrations of Mn, Si and Bof the dielectric layer 11. With the structure, the sinteringcharacteristic of the reverse pattern layer 17 gets higher. And, thedifference of the contraction in sintering gets smaller between thereverse pattern layer 17 and the internal electrode layer 12. Therefore,the occurrence of the clearance between the end of the internalelectrode layer 12 and the reverse pattern layer 17 is be suppressed. Inthis case, the intrusion of the water component is suppressed, and thehumidity resistance is improved. Therefore, the life characteristic ofthe dielectric layer 11 is improved, and the reliability of themultilayer ceramic capacitor 100 is improved.

When Mn, Si and B diffuse from the reverse pattern layer 17 during thefiring, the concentrations of Mn, Si and B of the whole of the endmargin region 15 and the side margin region 16 are higher than those ofthe dielectric layer 11 in the capacity region 14. In this case, thedifference of the contraction in sintering gets smaller between the endmargin region 15 or the side margin region 16 and the capacity region14.

When the donor element amount of the reverse pattern layer 17 isexcessively large, the abnormal grain growth and the delay of sinteringat the surface of the multilayer chip 10 may not be necessarilysuppressed sufficiently. And so, it is preferable that the donor elementconcentration of the reverse pattern layer 17 has an upper limit. In theembodiment, as an example, when Mo is used as the donor element, it ispreferable that the Mo concentration in the reverse pattern layer 17with respect to the main component ceramic of the reverse pattern layer17 is less than 0.2 atm %. It is more preferable that the Moconcentration is 0.1 atm % or less. In this case, the concentration (atm%) is a concentration on a presumption that a B site of the maincomponent ceramic having the perovskite structure expressed by a generalformula ABO₃ is 100 atm %. In the following description, theconcentration (atm %) is a concentration on a presumption that a B siteof the main component ceramic having the perovskite structure expressedby a general formula ABO₃ is 100 atm %.

In the embodiment, the donor element concentration in the end marginregion 15 and the side margin region 16 with respect to the maincomponent ceramic of the end margin region 15 and the side margin region16 is lower than the donor element concentration in the dielectric layer11 in the capacity region 14 with respect to the main component ceramicof the dielectric layer 11 in the capacity region 14. However, therelationship of the concentrations is not limited. For example, thedonor element concentration in one of margin regions with respect to themain component ceramic of the one of margin regions may be lower thanthe donor element concentration in the dielectric layer 11 in thecapacity region 14 with respect to the main component ceramic of thedielectric layer 11 in the capacity region 14.

Next, when a Mn amount in the reverse pattern layer 17 is excessivelylarge, the capacity of the capacity region 14 may be reduced because ofdiffusion of Mn into the dielectric layer 11 in the capacity region 14.And so, it is preferable that the Mn concentration in the reversepattern layer 17 has an upper limit. In the embodiment, as an example,it is preferable that the Mn concentration in the reverse pattern layer17 is 2.5 atm % or less. On the other hand, when the Mn amount in thereverse pattern layer 17 is excessively small, high sinteringcharacteristic is not achieved in the reverse pattern layer 17 and aclearance may occur between the end of the internal electrode layer 12and the reverse pattern layer 17 because of grain growth. In this case,life characteristic of the dielectric layer 11 may be degraded. And so,it is preferable that the Mn concentration in the reverse pattern layer17 has a lower limit. In the embodiment, as an example, it is preferablethat the Mn concentration in the reverse pattern layer 17 is 0.5 atm %or more.

When a Si amount in the reverse pattern layer 17 is excessively large, agrain growth region of the reverse pattern layer 17 reaches near the endof the internal electrode layer 12 and a structural defect may occur inthe internal electrode layer 12 because of stress in the internalelectrode layer 12. In this case, the life characteristic may bedegraded. And so, it is preferable that the Si concentration in thereverse pattern layer 17 has an upper limit. In the embodiment, as anexample, it is preferable that the Si concentration in the reversepattern layer 17 is 2.5 atm % or less. On the other hand, when the Siamount in the reverse pattern layer 17 is excessively small, highsintering characteristic is not achieved in the reverse pattern layer 17and a clearance may occur between the end of the internal electrodelayer 12 and the reverse pattern layer 17. In this case, lifecharacteristic of the dielectric layer 11 may be degraded. And so, it ispreferable that the Si concentration in the reverse pattern layer 17 hasa lower limit. In the embodiment, as an example, it is preferable thatthe Si concentration in the reverse pattern layer 17 is 1.2 atm % ormore.

When a B amount in the reverse pattern layer 17 is excessively large,the grain growth region of the reverse pattern layer 17 reaches near theend of the internal electrode layer 12 and a structural defect may occurin the internal electrode layer 12 because of stress in the internalelectrode layer 12. In this case, the life characteristic may bedegraded. And so, it is preferable that the B concentration in thereverse pattern layer 17 has an upper limit. In the embodiment, as anexample, it is preferable that the B concentration in the reversepattern layer 17 is 0.3 atm % or less. On the other hand, when the Bamount in the reverse pattern layer 17 is excessively small, highsintering characteristic is not achieved in the reverse pattern layer 17and a clearance may occur between the end of the internal electrodelayer 12 and the reverse pattern layer 17. In this case, lifecharacteristic of the dielectric layer 11 may be degraded. And so, it ispreferable that the B concentration in the reverse pattern layer 17 hasa lower limit. In the embodiment, as an example, it is preferable thatthe B concentration in the reverse pattern layer 17 is 0.15 atm % ormore.

In the embodiment, the concentrations of Mn, Si and B in the end marginregion 15 and the side margin region 16 are higher than theconcentrations of Mn, Si and B in the dielectric layer 11 in thecapacity region 14. However, the relationship of the concentrations isnot limited. For example, the concentrations of Mn, Si and B in one ofmargin regions may be higher than the concentrations of Mn, Si and B inthe dielectric layer 11 in the capacity region 14.

Next, a description will be given of a manufacturing method of themultilayer ceramic capacitor 100. FIG. 5 illustrates a manufacturingmethod of the multilayer ceramic capacitor 100.

(Making process of raw material powder) A dielectric material forforming the dielectric layer 11 is prepared as illustrated in FIG. 5.Generally, an A site element and a B site element are included in thedielectric layer 11 in a sintered phase of grains of ABO₃. For example,BaTiO₃ is tetragonal compound having a perovskite structure and has ahigh dielectric constant. Generally, BaTiO₃ is obtained by reacting atitanium material such as titanium dioxide with a barium material suchas barium carbonate and synthesizing barium titanate. Various methodscan be used as a synthesizing method of the ceramic structuring thedielectric layer 11. For example, a solid-phase method, a sol-gelmethod, a hydrothermal method or the like can be used. The embodimentmay use any of these methods.

An additive compound may be added to resulting ceramic powders, inaccordance with purposes. The additive compound may be an oxide of Mn, V(vanadium), Cr (chromium) or a rare earth element (Y (yttrium), Sm(samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy(dysprosium), Ho (holmium), Er (erbium), Tm (thulium) and Yb(ytterbium)), or an oxide of Co (cobalt), Ni, Li (lithium), B, Na(sodium), K (potassium) and Si, or glass. In the embodiment, at leastone of donor elements is added to the resulting ceramic powders. And, inthe embodiment, at least Me source, Si source and B source are added tothe resulting ceramic powder.

In the embodiment, it is preferable that ceramic particles structuringthe dielectric layer 11 are mixed with compound including additives andare calcined in a temperature range from 820 degrees C. to 1150 degreesC. Next, the resulting ceramic particles are wet-blended with additives,are dried and crushed. Thus, ceramic powder is obtained. For example, itis preferable that an average grain diameter of the resulting ceramicpowder is 50 nm to 300 nm from a viewpoint of thickness reduction of thedielectric layer 11. The grain diameter may be adjusted by crushing theresulting ceramic powder as needed. Alternatively, the grain diameter ofthe resulting ceramic power may be adjusted by combining the crushingand classifying.

Next, a reverse pattern material for forming the end margin region 15and the side margin region 16 is prepared. An additive compound may beadded to ceramic powder obtained by the same process as the dielectricmaterial, in accordance with purposes. The additive compound may be anoxide of Mn, V, Cr or a rare earth element (Y, Sm, Eu, Gd, Tb, Dy, Ho,Er, Tm and Yb), or an oxide of Co, Ni, Li, B, Na, K and Si, or glass. Inthe embodiment, the donor element is not added to the resulting ceramicpowders. Alternatively, an amount of the donor element added to theresulting ceramic powders is less than an amount of the donor elementadded to the dielectric material. Moreover, in the embodiment, at leastthe Mn source, the Si source and the B source are added to the resultingceramic powder. The added amount of Mn, Si and B to the resultingceramic powder are larger than the added amount of Mn, Si and B to thedielectric material.

In the embodiment, it is preferable that ceramic particles structuringthe end margin region 15 and the side margin region 16 are mixed withcompound including additives and are calcined in a temperature rangefrom 820 degrees C. to 1150 degrees C. Next, the resulting ceramicparticles are wet-blended with additives, are dried and crushed. Thus,ceramic powder is obtained. For example, it is preferable that anaverage grain diameter of the resulting ceramic powder is 50 nm to 300nm, as well as the dielectric material. The grain diameter may beadjusted by crushing the resulting ceramic powder as needed.Alternatively, the grain diameter of the resulting ceramic power may beadjusted by combining the crushing and classifying.

(Stacking process) Next, a binder such as polyvinyl butyral (PVB) resin,an organic solvent such as ethanol or toluene, and a plasticizer areadded to the resulting dielectric material and wet-blended. With use ofthe resulting slurry, a strip-shaped dielectric green sheet with athickness of 0.8 μm or less is coated on a base material by, forexample, a die coater method or a doctor blade method, and then dried.

Then, a pattern (first pattern) of the internal electrode layer 12 isprovided on the surface of the dielectric green sheet by printing metalconductive pastes for forming an internal electrode with use of screenprinting or gravure printing. The conductive pastes include an organicbinder. A plurality of patterns are alternatively exposed to the pair ofexternal electrodes. As co-materials, ceramic particles are added to themetal conductive pastes. A main component of the ceramic particles isnot limited. However, it is preferable that the main component of theceramic particles is the same as that of the dielectric layer 11. Forexample, BaTiO₃ of which an average particle size is 50 nm or less isevenly dispersed.

Next, a binder and an organic solvent are added to the reverse patternmaterial. The binder is such as ethyl cellulose. The organic solvent issuch as terpineol. And the reverse pattern material is kneaded with thebinder and the organic solvent by a roll mill. Thus, a reverse patternpastes are obtained. The reverse pattern paste is printed on acircumference area of the dielectric green sheet. The circumference areais a part of the dielectric green sheet where the internal electrodelayer pattern is not printed. The reverse pattern acts as a reversepattern (second pattern). Therefore, a level difference caused by theinternal electrode layer pattern is buried.

Then, the dielectric green sheet on which the internal electrode layerpattern and the reverse pattern are printed is stamped into apredetermined size, and a predetermined number (for example, 100 to 500)of stamped dielectric green sheets are stacked while the base materialis peeled so that the internal electrode layers 12 and the dielectriclayers 11 are alternated with each other and the end edges of theinternal electrode layers 12 are alternately exposed to both end facesin the length direction of the dielectric layer 11 so as to bealternately led out to a pair of external electrodes 20 a and 20 b ofdifferent polarizations. Cover sheets, which are to be the cover layers13, are stacked on the stacked dielectric green sheets and under thestacked dielectric green sheets. The resulting compact is cut into apredetermined size (for example, 1.0 mm×0.5 mm). After that the binderis removed in N₂ atmosphere in a temperature range from 250 degrees C.to 500 degrees C. After that, metal conductive paste to be the externalelectrodes 20 a and 20 b are coated on the both end faces of the cutmultilayer structure and are dried. Thus, a compact of the multilayerceramic capacitor 100 is obtained.

(Firing process) The resulting compact is fired for ten minutes to 2hours in a reductive atmosphere having an oxygen partial pressure of10⁻⁵ to 10⁻⁸ atm in a temperature range of 1100 degrees C. to 1300degrees C. Thus, each compound of the dielectric green sheet is sinteredand grown into grains. In this manner, it is possible to manufacture themultilayer ceramic capacitor 100.

(Re-oxidizing process) After that, a re-oxidizing process may beperformed in N₂ gas atmosphere in a temperature range of 600 degrees C.to 1000 degrees C.

(Plating process) After that, with a plating process, a metal such asCu, Ni, and Sn may be coated on the external electrodes 20 a and 20 b.

In the manufacturing method of the embodiment, the donor elementconcentration of the reverse pattern material with respect to the maincomponent ceramic of the reverse pattern material is lower than thedonor concentration of the dielectric material with respect to the maincomponent ceramic of the dielectric material. In this case, abnormalgrain growth or delay of sintering at the surface of the multilayer chip10 is suppressed. Thereby, structural defect is suppressed. Therefore,the reliability of the multilayer ceramic capacitor 100 is improved.

In the manufacturing method of the embodiment, the concentrations of Mn,Si and B of the reverse pattern material with respect to the maincomponent ceramic of the reverse pattern material are higher than theconcentrations of Mn, Si and B of the dielectric material with respectto the main component ceramic of the dielectric material. In this case,the sintering characteristic of the reverse pattern layer 17 getshigher. And, the difference of the contraction in sintering gets smallerbetween the reverse pattern layer 17 and the internal electrode layer12. That is, the difference of the contraction in sintering gets smallerbetween the end margin region 15 or the side margin region 16, and thecapacity region 14. Therefore, the occurrence of the clearance betweenthe end of the internal electrode layer 12 and the reverse pattern layer17 is suppressed. In this case, the intrusion of the water component issuppressed, and the humidity resistance is improved. Therefore, the lifecharacteristic of the dielectric layer 11 is improved, and thereliability of the multilayer ceramic capacitor 100 is improved.

When the donor element amount of the reverse pattern material isexcessively large, the abnormal grain growth and the delay of sinteringat the surface of the multilayer chip 10 may not be necessarilysuppressed sufficiently. And so, it is preferable that the donor elementconcentration of the reverse pattern material has an upper limit. In theembodiment, as an example, when Mo is used as the donor element, it ispreferable that the Mo concentration of the reverse pattern materialwith respect to the main component ceramic of the reverse patternmaterial is less than 0.2 atm %. It is more preferable that the Moconcentration is 0.1 atm % or less. It is still more preferable that theMo concentration is zero.

Next, when the Mn amount in the reverse pattern material with respect tothe main component ceramic of the reverse pattern material isexcessively large, the capacity of the capacity region 14 may be reducedbecause of diffusion of Mn into the dielectric layer 11 in the capacityregion 14. And so, it is preferable that the Mn concentration in thereverse pattern material with respect to the main component ceramic ofthe reverse pattern material has an upper limit. In the embodiment, asan example, it is preferable that the Mn concentration in the reversepattern material is 2.5 atm % or less. On the other hand, when the Mnamount in the reverse pattern material with respect to the maincomponent ceramic of the reverse pattern material is excessively small,high sintering characteristic is not achieved in the reverse patternlayer 17 and a clearance may occur between the end of the internalelectrode layer 12 and the reverse pattern layer 17 because of graingrowth. In this case, life characteristic of the dielectric layer 11 maybe degraded. And so, it is preferable that the Mn concentration in thereverse pattern material with respect to the main component ceramic ofthe reverse pattern material has a lower limit. In the embodiment, as anexample, it is preferable that the Mn concentration in the reversepattern material is 0.5 atm % or more. From a viewpoint of achievingboth preferable capacity and preferable life characteristic of thedielectric layer 11, it is preferable that the Mn concentration in thereverse pattern material is 2.25 atm %±0.25 atm %.

When the Si amount in the reverse pattern material with respect to themain component ceramic of the reverse pattern material is excessivelylarge, the grain growth region of the reverse pattern layer 17 reachesnear the end of the internal electrode layer 12 and the structuraldefect may occur in the internal electrode layer 12 because of stress inthe internal electrode layer 12. In this case, the life characteristicmay be degraded. And so, it is preferable that the Si concentration inthe reverse pattern material with respect to the main component ceramicof the reverse pattern material has an upper limit. In the embodiment,as an example, it is preferable that the Si concentration in the reversepattern material with respect to the main component ceramic of thereverse pattern material is 2.5 atm % or less. On the other hand, whenthe Si amount in the reverse pattern material with respect to the maincomponent ceramic of the reverse pattern material is excessively small,high sintering characteristic is not achieved in the reverse patternlayer 17 and a clearance may occur between the end of the internalelectrode layer 12 and the reverse pattern layer 17. In this case, lifecharacteristic of the dielectric layer 11 may be degraded. And so, it ispreferable that the Si concentration in the reverse pattern materialwith respect to the main component ceramic of the reverse patternmaterial has a lower limit. In the embodiment, as an example, it ispreferable that the Si concentration in the reverse pattern material is1.5 atm % or more. From a viewpoint of achieving both suppression ofgrain growth and preferable sintering characteristic of the reversepattern layer 17, it is preferable that the Si concentration in thereverse pattern material is 2.25 atm %±0.25 atm %.

When the B amount in the reverse pattern material with respect to themain component ceramic of the reverse pattern material is excessivelylarge, the grain growth region of the reverse pattern layer 17 reachesnear the end of the internal electrode layer 12 and a structural defectmay occur in the internal electrode layer 12 because of stress in theinternal electrode layer 12. In this case, the life characteristic maybe degraded. And so, it is preferable that the B concentration in thereverse pattern material with respect to the main component ceramic ofthe reverse pattern material has an upper limit. In the embodiment, asan example, it is preferable that the B concentration in the reversepattern material with respect to the main component ceramic of thereverse pattern material is 0.3 atm % or less. On the other hand, whenthe B amount in the reverse pattern material with respect to the maincomponent ceramic of the reverse pattern material is excessively small,high sintering characteristic is not achieved in the reverse patternlayer 17 and a clearance may occur between the end of the internalelectrode layer 12 and the reverse pattern layer 17. In this case, lifecharacteristic of the dielectric layer 11 may be degraded. And so, it ispreferable that the B concentration in the reverse pattern material withrespect to the main component ceramic of the reverse pattern materialhas a lower limit. In the embodiment, as an example, it is preferablethat the B concentration in the reverse pattern material is 0.2 atm % ormore. From a viewpoint of achieving both suppression of grain growth andpreferable sintering characteristic, it is preferable that the Bconcentration in the reverse pattern material is 0.25 atm %±0.05 atm %.

EXAMPLES

The multilayer ceramic capacitors in accordance with the embodiment weremade and the property was measured.

Examples 1 to 11

(Making of the dielectric material) MoO₃, Ho₂O₃, MnCO₃, SiO₂ and B₂O₃were weighed so that the Mo concentration, the Ho concentration, the Mnconcentration, the Si concentration and the B concentration with respectto 100 atm % of barium titanate powder (an average grain diameter of 0.1μm) were respectively 0.20 atm %, 0.75 atm %, 0.08 atm %, 1.15 atm % and0.13 atm %. And the barium titanate powder was sufficiently wet-blendedwith MoO₃, Ho₂O₃, MnCO₃, SiO₂ and B₂O₃ and crushed with a ball mill.Thus, the dielectric material was obtained.

(Making of the reverse pattern material) In the examples 1 to 11, Ho₂O₃was weighed so that the Ho concentration with respect to 100 atm ofbarium titanate powder (an average grain diameter of 0.1 μm) was 0.75atm %. In the example 11, MoO₃ was weighed so that the Mo concentrationin the reverse pattern material was 0.10 atm %. MnCO₃ was weighed sothat the Mn concentration in the reverse pattern material was 2.25 atm %in the example 1, 2.00 atm % in the example 2, 2.50 atm % in the example3, 3.00 atm % in the example 4, 2.25 atm % in the examples 5 to 11. SiO₂was weighed so that the Si concentration in the reverse pattern materialwas 2.00 atm % in the examples 1 to 4, 1.50 atm % in the example 5, 2.50atm % in the example 6, 3.00 atm % in the example 7, 2.00 atm % in theexamples 8 to 11. B₂O₃ was weighed so that the B concentration in thereverse pattern material was 0.25 atm % in the example 1 to 7, 0.20 atm% in the example 8, 0.30 atm % in the example 9, 0.50 atm % in theexample 10, 0.25 atm % in the example 11. After that, the bariumtitanate powder was sufficiently wet-blended with MoO₃, Ho₂O₃, MnCO₃,SiO₂ and B₂O₃ and crushed with a ball mill. Thus, the reverse patternmaterial was obtained.

(Making of reverse pattern paste) As the organic binder, ethyl cellulosewas added to the reverse pattern material. As a solvent, terpineol wasadded to the reverse pattern material. And the reverse pattern material,the organic binder and the solvent were kneaded by a roll mill. Thus,the reverse pattern paste was obtained.

(Making of a multilayer ceramic capacitor) Butyral acting as an organicbinder, and toluene and ethyl alcohol acting as a solvent were added tothe dielectric material. A dielectric green sheet was formed by a doctorblade method so that the thickness of the green sheet was 1.2 μm.Conductive paste for forming an internal electrode was screen-printed onthe resulting green sheet. The reverse pattern paste was screen-printedon a part of the green sheet where the conductive paste was not printed.Thus, the level difference was suppressed. 250 numbers of the sheets onwhich the conductive paste for forming an internal electrode and thereverse pattern material were printed were stacked. Cover sheets havinga thickness of 30 μm were stacked on a lower face and an upper face ofthe stacked sheets. After that, a multilayer structure was obtained by athermo compression bonding. And the resulting multilayer structure wascut into a predetermined shape. The binder was removed in N₂ atmosphere.Ni external electrodes were formed on the resulting multilayer structureby a dip method. The resulting multilayer structure was fired at 1250degrees C. in a reductive atmosphere (O₂ partial pressure: 10⁻⁵ to 10⁻⁸atm). And sintered multilayer structure was formed. A length was 0.6 mm.A width was 0.3 mm. A height was 0.3 mm. The sintered multilayerstructure was re-oxidized in a N₂ atmosphere at 800 degrees C. Afterthat, metals of Cu, Ni and Sn were coated on a surface of externalelectrode terminals by plating. And, a multilayer ceramic capacitor wasformed. After firing, the thickness of the Ni internal electrode layers12 was 1.0 μm.

Comparative Example 1

In the comparative example 1, in the making process of the reversepattern material, Ho₂O₃, MnCO₃, SiO₂ and B₂O₃ were weighed so that theHo concentration, the Mn concentration, the Si concentration and the Bconcentration with respect to 100 atm % of barium titanate powder (anaverage grain diameter of 0.1 μm) were respectively 0.75 atm %, 2.25 atm%, 1.00 atm % and 0.25 atm %. Other conditions were the same as theexamples 1 to 11.

Comparative Example 2

In the comparative example 2, in the making process of the reversepattern material, Ho₂O₃, MnCO₃, SiO₂ and B₂O₃ were weighed so that theHo concentration, the Mn concentration, the Si concentration and the Bconcentration with respect to 100 atm % of barium titanate powder (anaverage grain diameter of 0.1 μm) were respectively 0.75 atm %, 2.25 atm%, 2.00 atm % and 0.10 atm %, Other conditions were the same as theexamples 1 to 11.

(Analysis) A HALT (Highly Accelerated Limit Test) defect rate and acapacity acquisition rate were measured with respect to the examples 1to 11 and the comparative examples 1 and 2. HALT tests of 125 degreesC.-15 Vdc-120 min-100 numbers were performed. Samples whose short defectrate was less than 10% were determined as acceptance (◯). Samples whoseshort defect rate was less than 20% and 10% or more were determined as(Δ). Samples whose short defect rate was 20% or more were determined asnot acceptance (×). A capacity was measured by an LCR meter in themeasuring of the capacity acquisition rate. Measured values werecompared with a design value that was calculated from a dielectricconstant of a dielectric material (a dielectric constant was calculatedby making a disc-shaped sintered material having a size of ϕ=10 mm×T=1mm from only a dielectric material in advance and measuring acapacitance), a crossing area of internal electrodes, a thickness of adielectric ceramic layer and stack number. When a capacity acquisitionrate (measured value/design value×100) was 90% to 105%, it wasdetermined as acceptance (◯). When the capacity acquisition rate wasless than 90% was determined as triangle (Δ).

Table 1 shows measured results. In the examples 1 to 11, the HALT defectrate was less than 20%. It is thought that this was because: thelifetime of the dielectric layer 11 got longer, the abnormal graingrowth or the delay of sintering at the surface of the multilayer chip10 was suppressed and the structural defect was suppressed because theMo concentration in the reverse pattern material with respect to themain component ceramic of the reverse pattern material was lower thanthe Mo concentration in the dielectric material with respect to the maincomponent ceramic of the dielectric material; and the sinteringcharacteristic of the reverse pattern layer 17 got higher and thedifference of contraction in sintering between the reverse pattern layer17 and the internal electrode layer 12 was reduced because theconcentrations of Mn, Si and B of the reverse pattern material werehigher than the concentrations of Mn, Si and B of the dielectricmaterial. On the other hand, in the comparative examples 1 and 2, theHALT defect rate was 20% or more. It is thought that this was becausethe sintering characteristic of the reverse pattern layer 17 got lowerand the difference of contraction in sintering between the reversepattern layer 17 and the internal electrode layer 12 was notsufficiently reduced because the Si concentration in the reverse patternmaterial was lower than the Si concentration in the dielectric material,in the comparative example 1. It is thought that this was because thesintering characteristic of the reverse pattern layer 17 got lower andthe difference of contraction in sintering between the reverse patternlayer 17 and the internal electrode layer 12 was not sufficientlyreduced because the B concentration in the reverse pattern material waslower than the B concentration in the dielectric material, in thecomparative example 2.

TABLE 1 HALT CAPACITY COMPOSITION [atm %] DEFECT ACQUISITION Mo Ho Mn SiB RATE RATE DIELECTRIC MATERIAL 0.20 0.75 0.08 1.15 0.13 [%] [%] EXAMPLE1 REVERSE 0.00 0.75 2.25 2.00 0.25 1 ∘ 100 ∘ EXAMPLE 2 PATTERN 0.00 0.752.00 2.00 0.25 4 ∘ 101 ∘ EXAMPLE 3 MATERIAL 0.00 2.50 2 ∘ 95 ∘ EXAMPLE 40.00 3.00 0 ∘ 88 Δ EXAMPLE 5 0.00 0.75 2.25 1.50 0.25 7 ∘ 102 ∘ EXAMPLE6 0.00 2.50 3 ∘ 98 ∘ EXAMPLE 7 0.00 3.00 12 Δ 96 ∘ EXAMPLE 8 0.00 0.752.25 2.00 0.20 6 ∘ 102 ∘ EXAMPLE 9 0.00 0.30 4 ∘ 97 ∘ EXAMPLE 10 0.000.50 17 Δ 98 ∘ EXAMPLE 11 0.10 0.75 2.25 2.00 0.25 3 ∘ 97 ∘ COMPARATIVEREVERSE 0.00 0.75 2.25 1.00 0.25 20 x 103 ∘ EXAMPLE 1 PATTERNCOMPARATIVE MATERIAL 0.00 0.75 2.25 2.00 0.10 29 x 104 ∘ EXAMPLE 2

The capacity acquisition rates of the examples 1 to 3 were higher thanthe capacity acquisition rate of the example 4. From the result, it isthought that the diffusion of Mn into the dielectric layer 11 wassuppressed because the Mn concentration in the reverse pattern materialwas 2.5 atm % or less.

The HALT defect rates of the examples 1, 5 and 6 were lower than theHALT defect rate of the example 7. From the result, it is thought thatthe grain growth of the reverse pattern layer 17 was suppressed becausethe Si concentration in the reverse pattern material was 2.5 atm % orless. And from the result that the HALT defect rates of the examples 1and 5 to 7 were low, it is thought that high sintering characteristicwas achieved in the reverse pattern layer 17 because the Siconcentration in the reverse pattern material was 1.5 atm % or more.

The HALT defect rates of the examples 1, 8 and 9 were lower than theHALT defect rate of the example 10. From the result, it is thought thatthe grain growth in the reverse pattern layer 17 was suppressed becausethe B concentration in the reverse pattern material was 0.3 atm % orless. And, from the result that the HALT defect rates of the examples 1and 8 to 10 were low, it is thought that high sintering characteristicwas achieved in the reverse pattern layer 17 because the B concentrationin the reverse pattern material was 0.2 atm % or more.

Although the embodiments of the present invention have been described indetail, it is to be understood that the various change, substitutions,and alterations could be made hereto without departing from the spiritand scope of the invention.

What is claimed is:
 1. A multilayer ceramic capacitor comprising: amultilayer structure in which each of a plurality of dielectric layersand each of a plurality of internal electrode layers are alternatelystacked, a main component of the dielectric layers being ceramic, themultilayer structure having a rectangular parallelepiped shape, theplurality of internal electrode layers being alternately exposed to afirst end face and a second end face of the multilayer structure, thefirst end face facing with the second end face, wherein concentrationsof Mn, Si and B of a margin region with respect to a main componentceramic of the margin region are respectively higher than concentrationsof Mn, Si and B of the dielectric layers in the multilayer structurewith respect to a main component ceramic of the dielectric layers in themultilayer structure, wherein a donor element concentration of themargin region with respect to the main component ceramic of the marginregion is lower than a donor element concentration of the dielectriclayers in the multilayer structure with respect to the main componentceramic of the dielectric layers in the multilayer structure, whereinthe margin region is at least one of an end margin region and a sidemargin region, wherein, in the multilayer structure, the end marginregion is a region in which internal electrode layers exposed to thefirst end face are facing with each other without sandwiching aninternal electrode layer exposed to the second end face and a region inwhich internal electrode layers exposed to the second end face arefacing with each other without sandwiching an internal electrode layerexposed to the first end face, wherein, in the multilayer structure, theside margin is a region covering edge portions to which the plurality ofinternal electrode layers extend toward two side faces other than thefirst end face and the second end face.
 2. The multilayer ceramiccapacitor as claimed in claim 1, wherein the donor element is Mo.
 3. Themultilayer ceramic capacitor as claimed in claim 1, wherein the maincomponent ceramic of the margin region and the main component ceramic ofthe dielectric layers in the multilayer structure are barium titanate.4. The multilayer ceramic capacitor as claimed in claim 1, wherein amain component of the internal electrode layers is nickel.
 5. Amanufacturing method of a multilayer ceramic capacitor comprising: afirst process of providing a first pattern of metal conductive paste, ona green sheet including main component ceramic grains; a second processof making a stack unit by providing a second pattern of main componentceramic grains, around the first pattern on the green sheet; and a thirdprocess of stacking a plurality of the stack units formed in the secondprocess so that positions of the first patterns are alternately shiftedto each other and firing a ceramic multilayer structure of the stackunits, wherein concentrations of Mn, Si and B of the second pattern withrespect to a main component ceramic of the second pattern arerespectively higher than concentrations of Mn, Si and B of the greensheet with respect to a main component ceramic of the green sheet,wherein a donor element concentration of the second pattern with respectto the main component ceramic of the second pattern is lower than adonor element concentration of the green sheet with respect to the maincomponent ceramic of the green sheet.
 6. The method as claimed in claim5, wherein the donor element is Mo.
 7. The method as claimed in claim 6,wherein a Mo concentration of the second pattern with respect to a maincomponent ceramic of the second pattern is less than 0.2 atm %.
 8. Themethod as claimed in claim 5, wherein a Mn concentration of the secondpattern with respect to a main component ceramic of the second patternis 0.5 atm % or more and 2.5 atm % or less.
 9. The method as claimed inclaim 5, wherein a Si concentration of the second pattern with respectto a main component ceramic of the second pattern is 1.5 atm % or moreand 2.5 atm % or less.
 10. The method as claimed in claim 5, wherein a Bconcentration of the second pattern with respect to a main componentceramic of the second pattern is 0.2 atm % or more and 0.3 atm % orless.
 11. The method as claimed in claim 5, wherein a main componentceramic of the green sheet and the second pattern is barium titanate.12. The method as claimed in claim 5, wherein a main component metal ofthe first pattern is nickel.